The preparation of co-polymers of carbon monoxide and ethylenically unsaturated compounds, in which co-polymers the units originating from carbon monoxide alternate or substantially alternate with the units originating from the ethylenically unsaturated compounds, has been described in numerous patent publications, most of which deal with the preparation of the co-polymers in a liquid phase process.
These co-polymers can also be prepared by a gas phase process. In such a process the monomers are contacted with a catalyst composition based upon
(a) a compound of a metal of Group VIII of the Periodic Table; PA1 (b) an anion; and PA1 (c) a bidentate ligand PA1 (a) a source of cations of a metal of Group VIII of the Periodic Table; PA1 (b) a source of anions which comprise a plurality of boron atoms or a source of organic boron containing anions or an aluminoxane; and PA1 (c) a source of ligands. PA1 (a) a cation of a metal of Group VIII of the Periodic Table; PA1 (b) a boron containing anion selected from anions which contain a plurality of boron atoms and anions of the general formula BZ.sub.4.sup.- wherein each Z independently represents a substituted or unsubstituted hydrocarbyl group, or a borane of the general formula BZ.sup.1.sub.3 wherein each Z.sup.1 independently represents a substituted or unsubstituted hydrocarbyl group, or an aluminoxane; and PA1 (c) a ligand selected from PA1 (2) bidentate ligands of the general formula ##STR1## wherein X.sup.1 and X.sup.2 independently represent organic bridging groups each containing 3 or 4 atoms in the bridge at least 2 of which are carbon atoms, PA1 (3) bidentate ligands of the general formula EQU R.sup.5 S-Q-SR.sup.6 (III) PA1 (4) monodentate ligands of the general formula EQU R.sup.7 R.sup.8 R.sup.9 M.sup.3 (IV)
in the substantial absence of a liquid diluent, i.e. such that the gas phase forms the continuous phase.
Examples of such gas phase processes are known from EP-A-248483. An example of a suitable anion is the para-toluenesulphonate anion. The corresponding acid, in the exemplified case para-toluenesulphonic acid, is a suitable source of the anion.
The present Applicant has devoted a considerable amount of research towards improving the performance of the catalyst composition, for example by varying the type and the source of the anion used as catalyst component b). EP-A-508502 discloses that high activity catalysts for the gas phase process can be obtained by incorporating therein certain types of Lewis acids as component b). In EP-A-501576 the use of Lewis acid/Bronsted acid mixtures is recommended for that purpose.
The present invention provides improved catalysts for the gas phase process which comprise, as anions, anions containing a plurality of boron atoms, such as carborate anions, or organic boron containing anions, such as hydrocarbylborate anions. These anions are non- or weakly co-ordinating with the Group VIII metal and they are bulky. It is surprising that these anions give an improvement in catalyst activity in the gas phase process and an improvement in the molecular weight of the co-polymer obtained, as they fail to give improvements in liquid phase polymerizations carried out under otherwise similar conditions. It is also remarkable that neutral organic boranes, such as trihydrocarbylboranes can act as suitable source of anions. Aluminoxanes, when used as a source of anions, provide also catalyst compositions with attractive activity in the gas phase process.
Published Netherlands patent application 9001229 suggests the use of carborate anions as a catalyst component in the Group VIII metal catalyzed alternating co-polymerization of carbon monoxide with olefins. However, this document does not give any further details as regards the conditions of the use of the carborate anions and the benefits thereof. The document is concerned with liquid phase slurry polymerizations and it is entirely silent as regards gas phase processes. Brookhart et al. (J. Am. Chem. Soc. 114 (1992) p. 5894 and 116 (1994) p. 3641) have used the tetrakis 3,5-bis-(trifluoromethyl)phenyl!borate anion in combination with certain palladium/nitrogen bidentate complexes in the liquid phase synthesis of stereoregular co-polymers of carbon monoxide with styrene related olefins. EP-A-590942 discloses the use of certain aluminoxanes in Group VIII metal catalyzed liquid phase slurry polymerizations of carbon monoxide with ethene. The present favourable results are not deducible from any of these documents and are indeed surprising.
A study of the use of boron hydrocarbyl compounds as catalyst component in liquid phase copolymerizations of carbon monoxide with ethylenically unsaturated compounds is the subject matter of the earlier filed non-prepublished patent application EP-A-619335.